Another idea for later on, if its possible to add either unique tech or resources on Aiur / Char.
Perhaps tech and a unique crystal that unlocks the ability for players to build Photon Cannons / Pylons to power them.
Unlock triggers rather than tech, like "Destroy X number of Tier 5 Nexuses".
For Protoss it'd be somewhat easy on the art side, could potentially just use cyan-tinted Uranium as the resource?

For Char, perhaps integrate it with the biter capture tech, so maybe you have to capture a Zerg Queen or Hive, then ship the eggs back to Nauvis for cultivation (so you save on rocketry by producing the goods locally).
And perhaps with endless scaling swarm attacks (if scaled by units killed) it might be better to just do occasional "raids" to Char than setting up a permanent production line.
Naturally with the spoiling (hatching) mechanic so you risk spawning a Zerg base on Nauvis by accident.
For resources perhaps some creep-harvesting?

For Protoss, maybe each Pylon linearly increases the risk of protoss invasion forces (due to them tuning into the crystals energy or whatever).
Same with Zerg, each captured hive transported to Nauvis risks more Zerg invasions?
Stuff for the future!
Space Age brougth so many cool possibilities.

If any of this is possible without a lot of art work, would be cool.

Manufacture / production would be for a separated mod. :) This one focus on efficiently killing your base.

I do want to do the biter egg tech replacement later on. Right now, you can capture Hive / Nexus, and they turn into biter lol. It was done this way to preserve the biter techs when you are not playing with biters. Imagine having an ultralisk spawn from an larva egg or a dark templar spawn from a protoss crystal. Chaos ensure. =)

There will be interplanetary attacks in later version. There are a few end game subsystems which I have been disabled for Factorio 2.0 redesign.